Method For Determination Of Iodine Research Articles

Iodine determination in animal feed by inductively coupled plasma mass spectrometry – results of a collaborative study

ABSTRACT A collaborative study was conducted in order to fully validate the performance characteristics and to evaluate the suitability of a method for determination of iodine in animal feed. The method consists of an alkaline extraction in tetramethylammonium hydroxide (TMAH) solution followed by the determination of iodine by inductively coupled plasma-mass spectrometry (ICP-MS). The method was validated for different types of feed and feed materials with a broad concentration range of 0.65–622 mg I/kg. Good agreement was found between the overall mean mass fraction values from the collaborative trial (13.8 ± 1.3 mg I/kg and 0.657 ± 0.228 mg I/kg) and the values previously determined in proficiency tests for two of the test materials (12.65 ± 2.47 mg I/kg and 0.72 ± 0.22 mg I/kg) indicating satisfactory accuracy of the method. Reproducibility standard deviations were between 7.85% and 34.65% and the HorRat values were under the acceptable limit of 2 so the between-laboratory precision was considered acceptable. Based on the statistical evaluation of the results it was concluded that the method is suitable for its intended purpose; it has been accepted as European Standard EN17050:2017 by the European Committee for Standardisation (CEN).

Determination of iodine in geothermal water samples – preliminary ICP-MS method validation results

Abstract Iodine is a microelement which occurs in natural water in different concentrations dependent on water type, origin and total dissolved solids concentration. The objects of research were natural geothermal water. In this paper, the fitness of the inductively coupled plasma mass spectrometry (ICP-MS) method for iodine determination in water with higher temperatures was tested and selected methodological problems were discussed. Basic method parameters (precision, accuracy, linearity, uncertainty) were determined. Calculated statistical parameters of the validated method fulfil the assumed criteria. The received results (correlation coefficient equal to 0.999) show that the linearity of the ICP-MS method is good. The accuracy was expressed as recovery (R) and according to the literature is at an acceptable level. The results of precision assessments (RSD) also correspond to the literature data.

Determination of iodine in plants by ICP-MS after alkaline microwave extraction

Iodine is an essential element, important for normal thyroid function. Due to the frequency of health problems associated with its insufficient intake, new or additional sources of iodine have to be investigated. One of them could be iodine enriched plants. Before introduction into the human diet, the iodine content must be known as precisely as possible. A method of iodine determination in various plant samples by inductively coupled plasma mass spectrometry (ICP-MS) after alkaline microwave extraction was optimized. Among the tested ratios between TMAH and water, the ratio 1:5 was found to be optimal, using the following temperature program: 20min ramp to 200°C and 5min hold on 200°C. For measurements, 0.1% TMAH solution was chosen as optimal, using helium in the collision cell. A calibration line, for which standards were prepared in 0.1% TMAH, can be used for quantitative determination of iodine content. Measurement uncertainty was estimated to be around 30% for samples with low iodine content (around 0.2μgI/g) and below 7% for samples with higher iodine content (0.7μgI/g). Detection limits were 20ng/g of sample or less and good repeatability of the measurements and linearity over a wide concentration range were found. The results obtained by the optimized method were compared to those obtained with an independent method (k0-INAA), and they showed very good agreement, proving the accuracy of the determination by ICP-MS. Finally, iodine content was determined in samples with different matrices: pea seeds, pumpkin seeds and buckwheat achenes, from plants foliar sprayed with iodide or iodate solutions at the time of blooming.

Novel method for indirect determination of iodine in marine products by atomic fluorescence spectrometry

A method for the determination of iodine based upon compound H2HgI4, formed between I− and Hg2+ in nitric acid and extracted in methyl isobutyl ketone(MIBK), was developed via atomic fluorescence spectrometry(AFS). After the compound is reduced with potassium borohydrid(KBH4), the resultant mercury vapor was injected into the instrument and iodine was, therefore, indirectly determined. Experimental parameters such as the conditions of extraction reagents, aqueous phase acidity, elemental mercury diffusion temperature in a vial and other factors were investigated and optimized. Under the optimum experimental conditions, this method shows a detection limit of 0.038 μg/L iodine and a linear relationship between 0.04–20 μg/L. The method was applied to determining the iodine content in marine duck eggs, kelps, laver and Ganoderma lucidum spirulina, showing a relative standard deviation(RSD) of 2.15% and the recoveries in the range of 98.1%–102.5%.

Methods for determination of iodine in urine and salt

Good quality data on iodine concentrations in urine and salt samples are indispensable for the efficient management of national salt iodisation programmes and for evaluating iodine interventions. Most of the analytical methods for urinary iodine concentration are based on the manual spectrophotometric measurement of Sandell-Kolthoff reduction reaction catalysed by iodine using different oxidising reagents in the initial digestion step. Other analytical methods include semi-quantitative methods, a microplate method, automated methods; and the technologically advanced methods include the inductively coupled plasma mass-spectrometer method. Iodine in salt is determined quantitatively by the titration method, colorimetrically by the WYD iodine checker or by a technologically advanced potentiometric method. Worldwide, titration is the method of choice because of its accuracy, ease of operation and low cost. Rapid test kits are suitable for qualitative use in situations where iodised salt need to be distinguished from non-iodised salt, preferably with titration back-up.

Pressurised Extraction Using Dilute Ammonia: A Simple Method for Determination of Iodine in Soil, Sediment and Biological Samples by Inductively Coupled Plasma‐Mass Spectrometry

A simple sample treatment method for the accurate and precise determination of iodine in soil, sediment and biological samples by inductively coupled plasma‐mass spectrometry (ICP‐MS) is described. Iodine in samples was extracted in screw top PTFE‐lined stainless steel bombs using a 10% v/v ammonia solution at 185 C for 18 hours (overnight), after which the extract was introduced into the ICP‐MS for direct measurement. 126Te was employed as the internal standard to compensate for matrix effects and instrument drift. The limit of detection (LOD, three times the standard deviation of the procedural blank solution, expressed as the concentration in the sample solution) was 0.003 ng ml‐‐1. The limit of quantitation (LOQ, ten times the standard deviation of the procedural blank solution, expressed as the concentration in the solid samples, dilution factor DF = 100) was 0.01 μg g‐‐1 (dry mass). The accuracy and precision of the method were demonstrated by analysing different Chinese geological certified reference materials (soils, stream sediments and a hair sample). The measured concentrations were in a good agreement with the certified values indicating that bias in the method was not significant. The precision (n = 10) for different concentrations ranged from 1.82% to 4.32% RSD. Comparison of the ammonia extraction procedure with a “sintering” method indicated that there was no significant difference in results obtained with the two methods for geological soil and stream sediment samples. However, for biological samples, such as hair, kelp, tea etc., the results obtained by the sintering method were far below those of the ammonia extraction method. The ammonia extraction has advantages, as it is simpler than the “sintering” method, and has a lower procedural blank, better detection limits and reproducibility. Due to the simplicity of the method, a high rate of sample throughput is possible.

Optimization of iodine determination according to Schöniger

The method of iodine determination in organic compounds according to Schoniger [3, 4] was improved by using an alkaline absorption solution of DBH. In contrast to elemental bromine DBH is a stable and easy to handle crystalline compound. For the removal of the excess of DBH 5-sulfosalicylic acid (C7H6O6S × 2H2O [5965-83-3]) [5] is more suitable than formic acid [64-18-6]. Assays for the determination of 2-iodobenzoic acid in the range from 1 to 25 mg iodine are described. 32 organic iodine compounds, mostly x-ray contrast media, could be analyzed with a percentage relative standard deviation of about 0.2%.

Modification of a Nonincinerative Method for Determination of Iodine in Iodoproteins

Modification of a Nonincinerative Method for Determination of Iodine in Iodoproteins

Liquid Chromatographic Method for Determination of Iodine in Milk: Collaborative Study

Abstract Nine laboratories participated in an AOAC International/ International Dairy Federation collaborative study on a liquid chromatographic (LC) method for determination of iodine in milk. Liquid milk is passed through a 25 000 MW membrane filter to remove protein and insoluble material. Iodine (in the form of iodide) in the clear filtrate is separated by reversed-phase ion-pair LC and is detected electrochemically. Participants analyzed 2 commercial pasteurized whole milks and 5 nonfat dry milk powders in blind duplicate. Each sample was tested in duplicate on 2 days. Repeatability and reproducibility standard deviations (sr and SR, respectively) and repeatability and reproducibility relative standard deviations (RSDr and RSDR, respectively) for determinations of iodine in whole milk (mean recovery, 86.7%) were as follows: sr, 22 μg/L; SR, 22 μg/L; RSDr, 8.2%; and RSDR, 8.3%. For powdered milk (mean recovery, 91 %), the values were as follows: sr, 0.14 μg/g; SR, 0.22 μg/g; RSDr, 9.0%; and RSDR, 12.7%. The method was adopted first action by AOAC International.

The rapid determination of iodine in organic substances

A simple and rapid method for determination of iodine in highly iodized organic substances is described. The method involves oxygen flask combustion of the sample to be analyzed, formation of iodine in a molecular form, and use of a special multicomponent absorption solution containing sodium thiosulfate, phosphate buffer, pH 7.1–7.2, and starch. The quantity of absorbed iodine is determined by iodometric titration of the excess sodium thiosulfate in the absorption solution. The method affords a drastic reduction in the total length of analysis. The relative error of determination is not greater than 1%.

Determination of iodine in biological samples by resonance neutron activation

A method of iodine determination in biological samples by means of resonance neutron activation is described. This method has made it possible to determine the iodine content of such samples as children's thyroid gland, grass frog's skin, etc.

Roentgen ray fluorescence method for determination of iodine in tissue.

A roentgen ray fluorescence method was developed for the quantitative determination of iodine concentration in tissue. The method is based on the use of two beams, of which one excites the K roentgen rays of iodine, while the other does not. The concentration of iodine was determined from the difference between the counting rates of the fluorescent and the scattered radiation. The measurements were carried out with standard equipment consisting of a generator, a NaI)Tl)-detector and a scaler. An accuracy of 0.1 mg I per g was obtained with the radiation exposure of about 1 R.

Rapid Neutron Activation Method for Determination of Iodine in Milk

A simple method for determination of total iodine in milk, based on neutron activation analysis is described. After the irradiation, iodine is separated from the milk samples by a radiochemical procedure based on solvent extraction and precipitation, and 128I activity is subsequently measured with a gamma-ray spectrometer. Precision of the method at iodine concentrations of the order of 0.1ppm is about 5%.

A new routine method for determination of iodine in plant materials

A new method is suggested for determination of iodine in grass and crop samples. The sample is decomposed with sulphuric, nitric and perchloric acids. Iodine is determined in the diluted digest. The method is excellent for routine work, being faster and simpler than previous nethods.

A Method of Iodine Determination by Characteristic X-Ray Absorption

This paper describes a technique for the quantitative analysis of nonradioactive iodine. The method uses the X-ray absorption discontinuities for the detection of iodine in the presence of any other absorbing substance. A stationary lanthanum radiator converts an X-ray beam having a continuous spectrum into two monochromatic beams which straddle the iodine absorption edge. The energy spread is such as to make the technique relatively independent of other foreign elements. A rotating filter alternately absorbs one of the two beams while leaving the other on continuously. The information in the beams is detected and synchronously switched into two counting circuits. The intensity of the beams is measured by two counting-rate meters and the ratio of these intensities is obtained by a conventional self-balancing potentiometer. Since this ratio is determined every 1/60 of a second the iodine determination is insensitive to X-ray output, amplifier and detector drift.

Determination of iodine in milk

A method of iodine determination in milk is described. Dry ashing and extraction of the ash with water is followed by photometric determination of the catalytic influence on the Ce-As reaction. Distillation proves to be unnecessary. Determination with this method can be performed in any laboratory, though not specially equipped for trace analyses.

A Catalytic Method for Determination of Iodine

A Catalytic Method for Determination of Iodine